STM32H7 I/O port characteristics

[Kilian Nötzold]

Posted on May 23, 2018 at 11:32

Hello, I�m struggling understanding the I/O static characteristics for the STM32H7 devices.

I think that below 0.3xVdd a normal input is low and above 0.7xVdd it is high. But what is the meaning of the red marked lines?

Page 129

http://www.st.com/content/ccc/resource/technical/document/datasheet/group3/23/be/db/eb/29/39/4b/eb/DM00387108/files/DM00387108.pdf/jcr:content/translations/en.DM00387108.pdf

 

#stm32h7 #vil #vih

[Khouloud GARSI]

Posted on May 24, 2018 at 09:28

Hi

climbon

‌,

I think that below 0.3xVdd a normal input is low and above 0.7xVdd it is high. But what is the meaning of the red marked lines?

-> You're understanding is correct!

The red marked lines will be removed from the datasheet.

Thanks for bringing this to our attention and sorry for any inconvenience this may have caused.

Khouloud.

[Kilian Nötzold]

Posted on May 24, 2018 at 10:25

The red marked lines will be removed from the datasheet.

Thanks for the response it seems to be in all Datasheets of the STM32H7 Series. The questionable values (

0.4xVDD - 0.1 and 0.47xVDD + 0.25) are also shown in 'Figure 20. VIL/VIH for all I/Os except BOOT0' on page 130.

[Khouloud GARSI]

Posted on May 24, 2018 at 12:35

Correct, we have already checked this point and the fix will be done on the next release of the document.

We really appreciate your valuable contribution to the enhancement of our STM32 resources.

Khouloud.

[Khouloud GARSI]

Posted on May 29, 2018 at 16:47

Hi

Noetzold.Kilian

‌,

After further check, we found that the information shown on the datasheet are correct and will not be removed.

Actually, the first lines (colored in green) show the standard voltage values below/above them the input voltage is considered as low/high (general rule).

On the second lines (colored in red), we precise the voltage characteristics particularto the STM32H7 pins.

So, if you're using a voltage values above ''0.3*VDD'' but below ''0.4*VDD - 0.1'', the state of the pin is considered as low.

The same for the high state, if the voltage is above ''0.47*VDD + 0.25'', the state is high even if the voltage is below ''0.77*VDD''.

The two values are kept in order to show that using the STM32, we minimize the voltage interval in which the state of the pin is undetermined.

Hope this is clear and sorry for my first answer.

Khouloud.

[Kilian Nötzold]

Posted on June 01, 2018 at 10:12

Hi

Khouloud,

thank you for explaining!

Now I understood the purpose to but it is a bit confusing that the same Parameters have different Max/Min values and it is not clear that red overrules green. Maybe a footnote would be helpful.

Never the less at least the blue marked ''low'' should be ''high''.

Kilian

[Khouloud GARSI]

Posted on June 01, 2018 at 14:17

Hi Kilian,

I agree that this may lead to a confusion, I will highlight this point to our team and you will be updated about the taken action.

Regarding the blue mark, I have noticed this when trying to answer your question and already reported it. This will be rectified on the next release of the datasheet.

Thank you for reporting this!

Khouloud.